English to Persian (Farsi) Social Sciences Other Translation

Hi, here the author of a book is explaining why he actually revised the old book and didn't write a totally new one:
Another question was whether the content was
still relevant after 15 years in view of developments in the field. My subjective answer to
some soul-searching was that it was, as I have not found in the literature other concepts
and models of the same type to replace them. A somewhat less subjective and perhaps
more reliable answer is suggested by citation evidence.

Thank you very much in advance.